1. Field of the Invention
The present invention relates to downhole well recorders and methods of use thereof, and more particularly to methods of monitoring and collecting fluid dynamics data downhole in a well pipe, and to preprogrammed electronic recorders therefor which are installable in and retrievable from sidepocket mandrels.
2. Description of the Prior Art
The monitoring of fluid dynamics in oil wells and the like, during various operations such as production, fracturing and testing of wall integrity, require collection of data which are as accurate as possible, at various selected locations in a well. Some of the known techniques for monitoring well operations and developing the necessary data are discussed in an article entitled "New Technology Improved Monitoring Ability", appearing in the Oil and Gas Journal issue of May 8, 1989, at pages 43 and 44. Sensing surface pressure data is one known technique but does not give sufficiently accurate data since it inherently is unable to account for viscosity, density and friction losses as they occur downhole and data sensed at the surface must be extrapolated to even approximate downhole conditions. Placing pressure and temperature sensors downhole in a so-called dead string or wireline manner is also known but the suspension means can interfere with the operation of the well and can also prove cumbersome. Wireline placement of sensors also cannot satisfactorily develop data as to fluid dynamics externally of the well pipe.
Another disadvantage of wireline placement of sensors downhole is that such tend to restrict flow in the well pipe and are also subject to being adversely affected by some well stimulation materials which can be highly abrasive and highly corrosive.
Also known, such as disclosed in More U.S. Pat. No. 4,216,536, for example, are monitoring systems which place sensors downhole and transmit data recorded downhole up to the drilling platform using pressure pulses in the mud circulated through the drill string, a technique known as Mud Pulse Telemetry (MPT). In such a system, data is sensed and stored in a downhole microprocessor when the mud is not circulating and the data is subsequently transmitted to the surface while the mud is circulating. Alternatively, the data sensed downhole can be transmitted to the surface in real time using MPT, which data is then later compared for accuracy with the data as recorded downhole.